Search Results (1,863)

Hydrogen storage and separation remain major technical challenges limiting the broader implementation of hydrogen-based energy systems. Metal–hydride alloys offer a promising solution because they enable reversible hydrogen storage within their crystal structure and can selectively absorb hydrogen from multicomponent gas mixtures. However, the practical application of metal–hydride systems requires storage vessels that combine sufficient mechanical strength with effective heat removal, as hydrogen absorption is accompanied by significant heat generation that can reduce the reaction rate and usable storage capacity. This study addresses hydrogen storage within the crystal structure of metal alloys and introduces the potential of metal–hydride (MH) alloys for hydrogen separation from gas mixtures. It subsequently presents the structural design and strength assessment of a low-pressure, double-walled, tubular steel MH storage vessel intended for hydrogen storage in a MnTiVFeZr-based alloy. Structural simulations were performed in ANSYS 2025 R2 Static Structural at three operating pressures: 3, 5, and 7 MPa. For all three simulated pressure conditions, the gravimetric hydrogen storage capacity of the alloy was 0.992 ± 0.016 wt.%. Following the selection of the most suitable design with an operating pressure of 3 MPa, an analytical calculation was performed to verify the results obtained from the numerical analysis. The storage vessel was subsequently manufactured and subjected to experimental strength validation using the test procedures specified in the STN EN 13322-2 standard. The design of the low-pressure tubular steel MH storage vessel also incorporates an efficient thermal management system based on a combination of active and passive cooling modules. The passive cooling module takes the form of an internal heat-transfer enhancement element, which is inserted into the primary storage vessel together with the MH alloy. The active cooling module uses a coolant flowing around the outer wall of the primary vessel. The optimal design of the aluminium passive cooling module was selected from four variants based on a steady-state temperature-field analysis conducted in ANSYS CFX. The selected module was subsequently manufactured and integrated into the proposed storage vessel. The vessel equipped with the passive cooling element was then subjected to experimental temperature measurements during hydrogen absorption by the MH alloy. The experimentally obtained data were compared with the numerical simulation results to evaluate the temperature fields within the vessel and the heat dissipation from the core of the MH storage system during hydrogen absorption. The main contribution of this work is the development of a mechanically validated and thermally managed tubular metal–hydride vessel that integrates structural design, numerical optimisation, manufacturing, and full-scale experimental testing within a single methodology. The proposed approach provides a practical basis for the further development and scaling of low-pressure metal–hydride systems for hydrogen storage, purification, and separation applications. Full article

Aluminum alloy 6061 is widely used in the industrial field, but its poor corrosion resistance has a significant impact on the reliability of equipment components. To address the corrosion resistance issue of 6061 aluminum alloy, a novel Ti-Zr-V conversion coating was prepared on its surface in this study, and the conversion parameters were optimized. The morphology, element distribution and content, composition of compounds, and corrosion resistance of the prepared Ti-Zr-V conversion coating were comprehensively analyzed and evaluated using scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, copper sulfate spot test, and electrochemical experiments. The research results showed that the conversion parameters had a significant impact on the corrosion resistance of the conversion coating. The optimal conversion parameters were a pH value of 4.5 and a conversion time of 5 min, with the optimal addition amount of the auxiliary film former NaVO₃ being 0.6 g/L. Under these conditions, the Ti-Zr-V conversion coating prepared was relatively dense, with fewer grooves, the longest spot resistance time, and the best corrosion resistance. Its surface mainly consisted of titanium dioxide, zirconium dioxide, vanadium pentoxide, V₂O₃, aluminum oxide, and a small amount of fluoride compounds. Electrochemical analysis also demonstrated that the corrosion rate of TiZrVCC decreased by approximately 87.12% compared to the aluminum alloy 6061 substrate, providing a theoretical basis and technical support for the further promotion and use of aluminum alloy. Full article

To elucidate the effect of cyclic hot forging and short-time aging (HFSTA) on the wear resistance of a Cu-Cr-Zr alloy, samples in the as-received state (solution-treated at 1000 °C) and after 4 passes and 6 passes of cyclic HFSTA at 450 °C were prepared. The relationships between microstructure and properties were systematically analyzed. The results indicate that the cyclic HFSTA process did not change the main phase structure of the Cu matrix but significantly tailored the grain morphology, local misorientation, grain boundary character, and tribo-chemical behavior of the surface. The 4-passes sample possessed relatively high hardness, electrical conductivity, and favorable microstructural stability and was able to form a continuous and dense oxide protective film during friction, as demonstrated by the increase in hardness from 86 HV (as-received) to 195 HV, the decrease in average coefficient of friction (COF) from 0.65 to 0.50, and the reduction in wear rate from 13.3 × 10⁻⁴ mm³/(N·m) to 0.3 × 10⁻⁴ mm³/(N·m). The 6-passes sample exhibited slightly higher hardness, but the increased proportion of low-angle grain boundaries (LAGBs) intensified cracking and spallation on the wear track, causing the wear rate to rebound to approximately 8.2 × 10⁻⁴ mm³/(N·m). The study demonstrates that the wear resistance of the Cu-Cr-Zr alloy does not improve monotonically with hardness or grain refinement but is jointly controlled by precipitation strengthening, dislocation/substructure strengthening, surface damage tolerance, and the stability of the tribo-film. For the dry sliding service conditions of Cu-Cr-Zr alloys, 4 passes of cyclic HFSTA at 450 °C represent an optimal processing window that balances mechanical properties, electrical conductivity, and wear resistance, providing guidance for the process optimization of components such as contact wires and welding electrodes. Full article

Cross-contamination during metal powder blending in multi-material laser powder bed fusion (PBF-LB/M) is a common production challenge and a key barrier to the wider industrial adoption of the process. In the present investigation, the effect of different CuCr1Zr foreign-particle cross-contamination rates of up to 5.0 wt.%, simulating different cross-contamination levels in an AlSi10Mg feedstock for PBF-LB/M, is examined. The resulting metallurgical features and tensile mechanical properties of the produced components were compared to those of reference specimens manufactured from uncontaminated powder. A microstructural analysis of CuCr1Zr contaminated samples revealed characteristic Cu-rich regions, demonstrating that the higher the level of cross-contamination is, the larger these regions are. Tensile yield stress is almost linearly increased with the contamination level while the opposite trend is noticed for tensile elongation at fracture. Two different stages of strain-hardening were noticed, with Stage I exhibiting a lower strain-hardening exponent, while higher strain-hardening exponents (>0.27) were noticed for Stage II, with the latter decreasing with increasing cross-contamination level. The tensile mechanical behaviour of PBF-LB/M specimens was evaluated for the first time with appropriate quality indices, which were initially developed for similar cast aluminium alloys. Overall, the quality index accounting for global tensile performance was decreased for all build directions with increasing cross-contamination level. Despite the lower quality index at the non-contamination level, the inclined (45°) printed specimens presented quality indices that were almost unaffected by the cross-contamination level. Full article

The effect of internal pressure on the layered microstructural evolution of N36 zirconium alloy cladding tubes was systematically studied under simulated loss-of-coolant accident (LOCA) biaxial creep conditions at 900 °C. The tested specimens were characterized by electron channeling contrast imaging, energy-dispersive X-ray spectroscopy, electron backscatter diffraction, and transmission electron microscopy. The results show that all specimens formed a typical layered cross-sectional structure consisting of an oxide film, an oxygen-rich α-Zr (α(O)) layer, and a prior-β transformed layer. The thickness of the α(O) layer and the oxygen diffusion depth changed markedly with internal pressure. The thickness of the α(O) layer was approximately 21 μm for the 0.8 MPa specimen and 11 μm for the 1.9 MPa specimen, respectively. The lower-pressure specimen exhibited a wider oxygen-affected region, whereas the higher-pressure specimen showed a steeper oxygen gradient. In the prior-β transformed layer, lath-like α structures formed under both conditions, but their spatial arrangement and orientation distribution were different. Under lower internal pressure, the laths were more regularly arranged and showed a more complete colony structure. Under higher internal pressure, the laths were more interwoven, and the orientation distribution became more scattered. Meanwhile, the high-pressure specimen retained a higher local orientation gradient and a higher degree of lattice distortion. These results indicate that the above microstructural differences mainly arise from the effect of internal pressure on the high-temperature exposure history. A higher internal pressure causes earlier instability of the specimen, thereby shortening the effective time for oxygen diffusion and microstructural evolution, rather than directly changing the oxidation or phase transformation process. Full article

This study develops novel multicomponent Al–Mg–Si–Zr–Cu-based alloys for high-pressure die casting (HPDC) with improved mechanical properties and thermal stability. Four compositions were designed through Zn and Cr additions, supported by thermodynamic modelling. XRD and SEM/EDS analysed phase formation and microstructure, while density, electrical conductivity, hardness, and mechanical behaviour under tensile and compressive loading at room temperature and 200 °C were evaluated. Hardness increased from 166 to 214 HV3 with Zn and Cr due to the formation of complex intermetallic phases. The Al–Mg–Si–Zr–Cu alloy showed the best balance of strength and ductility under tensile loading, whereas Zn and Cr additions reduced tensile performance. In compression, Zn significantly improved strength, reaching the ultimate compressive strength of 697 MPa. Compared with the reference AlSi9Cu3 alloy, the new alloys achieved up to 30% higher yield strength, 13% higher ultimate tensile strength, and improved thermal stability. Among the studied compositions, Al72Mg10Si5Zr3Cu10 showed the best overall performance, while Al67Mg10Si5Zr3Cu10Zn10 was optimal for compression-dominated applications. Full article

Thermomechanical processing (TMP) is of critical importance for tailoring microstructures and properties of high-strength titanium alloys and their composites. In this study, mechanical response and microstructural evolution mechanisms of 2 vol.% TiB/Ti-5Al-5Mo-5V-3Cr-1Zr (Ti-55531) matrix composites during isothermal compression at varied deformation temperatures (785–925 °C) and strain rates (0.001–1 s⁻¹) are comprehensively investigated by kinetic calculation and microstructural characterization. Strain-compensated constitutive equations in α + β and β phase regions were established. Results show that deformation temperature and strain rate influence flow behavior and microstructure through dynamic recovery (DRV) and dynamic recrystallization (DRX) of the β phase as well as dynamic spheroidization of the α phase. Crucially, three DRX mechanisms of β phase were identified, wherein TiB-induced β-DRX dominates, with α-assisted β-DRX and continuous dynamic recrystallization (CDRX) as secondary mechanisms. Dynamic spheroidization mechanisms of the α phase, including β-wedge penetration as well as α interaction and kinking, were elucidated. A comprehensive microstructural evolution mechanism map was constructed, and an optimized hot-processing window was proposed. Notably, the introduction of TiB significantly promotes β-DRX, which tends to randomize crystallographic orientations of the β phase, and enhances microstructural stability. This study provides theoretical complement and practical guidance for hot processing and microstructure control of metastable β titanium matrix composites. Full article

Chromium coatings with excellent corrosion resistance and strong Zr interfacial bonding are economical candidates for accident-tolerant fuel claddings. Irradiation-triggered elemental interdiffusion and interfacial voids severely degrade their service reliability. Ni alloying was introduced into the Cr matrix to obtain composite coatings with improved mechanical properties and irradiation resistance. CrNi coatings with different Ni contents were deposited using magnetron sputtering, whose microstructural features, phase composition, mechanical properties and irradiation behavior were comprehensively characterized by XRD, SEM, TEM and mechanical measurements. The pristine CrNi coatings display compact and uniform microstructural morphologies. Increasing Ni concentration significantly refines the columnar grain architecture and diminishes grain dimensions. Post-irradiation microstructural characterization reveals distinct structural evolution features of CrNi coatings with different Ni contents. Pure Cr and low-Ni coatings present enhanced XRD diffraction intensities and contain high-density irradiation-induced dislocation loops. The 27 at.% Ni coating after irradiation is indicative of irradiation-triggered local recrystallization and defect annihilation. Mechanical tests confirm that moderate Ni alloying (~17 at.%) achieves improved resistance to irradiation-induced hardening through solute–defect interaction effects, whereas excessive Ni (~27 at.%) degrades mechanical properties owing to aggravated lattice disorder, increased free volume, and soft Ni-phase dilution effects. Full article

Heat treatment significantly improves the ductility of additively manufactured Zr–2.5Nb alloy, but the mechanisms responsible for this improvement remain poorly understood. In this study, the effects of heat treatment on the microstructure and room-temperature tensile behavior of Zr–2.5Nb fabricated by laser powder bed fusion (LPBF) were investigated by comparing as-built (AB) and heat-treated (HT) specimens. The HT specimens were held at 800 °C for 2 h and subsequently air-cooled. A microstructure-based crystal plasticity fast Fourier transform (CPFFT) model was constructed directly from two-dimensional electron backscatter diffraction (EBSD) orientation and phase maps to quantify the local stress, strain, and slip responses of the α and β phases in the HT microstructure. Heat treatment caused the acicular α′ martensite to decompose, producing a coarser lamellar α + β microstructure. In a representative EBSD field of the HT specimen, β-Zr accounted for 6.0% of the analyzed area and was distributed predominantly between the α lamellae. Compared with the AB condition, heat treatment reduced the mean 0.2% proof stress and ultimate tensile strength from 840 and 1033 MPa to 792 and 881 MPa, respectively, while increasing the mean uniform strain from 4.02% to 6.94%. At an applied axial strain of 3.2%, the β/α ratios of phase-averaged equivalent strain and accumulated absolute slip were 1.59 and 2.51, respectively, whereas the corresponding ratios for von Mises stress and axial stress were 0.57 and 0.81. These results reveal pronounced stress–strain partitioning between the phases: β-Zr accommodated greater equivalent strain and more extensive slip, whereas α-Zr carried higher stresses. This interphase partitioning helps explain the increased uniform strain of the HT specimens, while the reduction in strength is primarily associated with α′-martensite decomposition and α-lamella coarsening. Full article

This work characterized the metallurgical properties and selected mechanical properties of the medical alloy Ti13Nb13Zr. The study included an analysis of the hardness and fracture toughness of the medical material, which was first solution heat-treated and then aged. This work significantly complements the literature on this alloy. This supplementation involved selecting previously unused heat treatment parameters: solution heat treatment from 1050 °C and subsequent aging in the range of 350 to 550 °C. After solution heat treatment from 1050 °C and quenching in water, the alloy is characterized by a microstructure composed of titanium martensite (α′) with low hardness and high fracture toughness. The applied aging process, which involves diffusion phenomena, involved the decomposition of α′ martensite and the precipitation of new α and β phases, resulting in increased hardness and decreased fracture toughness. The use of a previously unused solution heat treatment temperature of 1050 °C may additionally improve mechanical properties, including hardness and fracture toughness (K_IC), compared to lower solution heat treatment temperatures. The results obtained, using different heat treatment conditions, were confirmed by microstructural and phase analysis. This paper presents the characteristics of the tested alloy, a description of the heat treatment, and a detailed analysis of the phase transformations occurring during aging after solution heat treatment. Considerable attention was paid to fractographic analysis of fractures in samples obtained during fracture toughness tests. The obtained results significantly expand the knowledge of the tested alloy. Full article

To reveal the high-temperature hot deformation mechanism and optimize the thermal processing window of Zr-Nb alloy, hot compression tests were implemented via a thermal simulation apparatus over temperatures ranging from 500 to 900 °C and strain rates of 0.01~10 s⁻¹. The material’s flow performance, dynamic recrystallization (DRX) and phase transformation were systematically explored in this work. The results indicate that flow stress presents a negative correlation with deformation temperature and a positive correlation with strain rate. On the basis of measured stress–strain curves, the Arrhenius constitutive equation and processing map were established to quantitatively describe the alloy’s hot deformation behavior. Flow instability areas are mainly distributed in the low-temperature domain and the high strain rate region of medium-high temperature zones. The evolution of DRX under different strain rates and microstructural variations during phase transformation was analyzed in detail. Elevated strain rate leads to gradual grain refinement. Continuous dynamic recrystallization (CDRX) acts as the predominant DRX mode for Zr-Nb alloy, with merely minor discontinuous dynamic recrystallization (DDRX) features observed in the microstructure. Full article

Plasma electrolytic oxidation (PEO) is an effective method for developing protective conversion coatings on magnesium and its alloys. The efficiency of this process is governed by several factors, including electrical parameters and electrolyte composition. Typically, PEO has been performed in alkaline silicate or phosphate solutions, often enriched with simple fluoride ions (F⁻) to improve the mechanical and anticorrosive properties of the resulting layers. Recently, the positive impact of complex fluoride ions (such as ZrF₆²⁻, TiF₆²⁻, SiF₆²⁻, AlF₆³⁻ and PF₆⁻) on the properties of conversion coatings on magnesium substrates has been shown. This review analyzes how these complex precursors influence the phase composition, morphology, and corrosion resistance of coatings. Furthermore, these parameters are compared with those obtained by using electrolytes composed of a mixture of simple fluorides and additional constituents that provide the incorporation of the appropriate elements into the coating structure (phosphorus, silicon, zirconium, titanium, or aluminum). It was indicated that when using complex fluoride salts, an important aspect is the stability of the electrolyte, which depends on pH and the presence of stabilizing additives. Ensuring that the decomposition of the complex fluoride occurs during the PEO process increases the amount of fluorine incorporated into the layers formed, leading to the formation of a coating with enhanced properties. Full article

Ti6Al4V alloy is widely used in biomedical and engineering applications; however, its limited wear resistance and lack of intrinsic antibacterial activity restrict its long-term performance. Although multi-element nitride coatings prepared by cathodic arc evaporation (CAE) have shown considerable potential, the influence of substrate bias voltage on their microstructural evolution and multifunctional performance remains insufficiently understood. In this study, (TiCrCuZrAlAg)N multi-element nitride coatings were deposited on Ti6Al4V substrates by CAE under substrate bias voltages of 50, 100, and 150 V. The effects of bias voltage on coating composition, crystal structure, hardness, wear behavior, and antibacterial performance were systematically investigated. Increasing the bias voltage enhanced ion bombardment, leading to reduced coating thickness, lower Cu/Ag incorporation, and degraded crystallinity, which consequently affected coating performance. Among the investigated conditions, the coating deposited at 50 V exhibited the highest hardness (1628.4 HV), the lowest wear rate (0.08 × 10⁻⁷ g/m), and the highest antibacterial efficiency (99.2%). This study establishes a correlation between substrate bias voltage, microstructural evolution, and multifunctional performance in CAE-deposited (TiCrCuZrAlAg)N coatings, providing practical guidance for the design of multifunctional protective coatings. Full article

Four Al-Mg-Si alloys, three of them with additions of scandium or scandium and zirconium, were cast, homogenised at 550 °C, and precipitation hardened at 175 °C. For the alloy with the highest Sc content, significant discontinuous precipitation of Al₃Sc took place during cooling after casting. Homogenisation for 1 h led to the formation of Al₃Sc or Al₃(Sc,Zr) dispersoids. The Al₃(Sc,Zr) dispersoids were found in higher number densities than the Al₃Sc dispersoids, and the latter were not stable for longer homogenisation times. TEM observations indicate that the Al₃Sc or Al₃(Sc,Zr) dispersoids are not preferred nucleation sites for metastable (Mg,Si) particles. The precipitation hardening behaviour of the Al-Mg-Si alloys was not altered by the Sc or Sc+Zr additions. Full article

Growing attention in additive manufacturing (AM) of high-entropy alloys has intensified the demand for techniques in creating high-quality powder for AM. This study characterizes the effectiveness of a multifunctional vacuum arc melting (VAM) and ultrasonic-plasma atomization (UPA) system for creating TiZrNbHfTa powder. The focus is to evaluate the morphology, microstructural homogeneity, and phase composition of ultrasonically atomized powder to assess process capability for preparing powder feedstock for AM. Atomized powder was sieved into three size ranges, 15–63 µm, 63–125 µm, and 125–250 µm for characterization by scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), X-ray diffraction (XRD), and micro-computed tomography (micro-CT). SEM, EDS, and XRD results show that the powder is highly homogenous with an elemental distribution independent of powder size range and a microstructure comprising a BCC solid solution and minor monoclinic Ti oxide. Micro-CT scans indicate low porosity (0.24%, 0.08%, 0.24%) and high sphericity (0.93, 0.90, 0.93) for the 15–63 µm, 63–125 µm, and 125–250 µm distributions, respectively. Overall, the key innovation of this study is the successful application of ultrasonic atomization to produce high-quality TiZrNbHfTa refractory high-entropy alloy powder for additive manufacturing, a technique that has a limited scope of research. Specifically, this work demonstrates that ultrasonic atomization can produce highly homogeneous powder with high sphericity, low porosity, and a particle size distribution suitable for laser powder bed fusion and powder directed energy deposition, establishing ultrasonic atomization as a viable route for producing refractory high-entropy alloy powder for AM. Full article